1. Field of the Invention
The present invention relates to a tracing method by which tracing is carried out by designating a region by a wire limit, and more specifically, to a method by which a tracing direction can be arbitrarily changed in a single path.
2. Description of the Related Art
A method of tracing a model configuration by designating a region by a wire limit includes, for example, a method shown in FIG. 3(a). As shown in the figure, tracing is carried out along a path 12a in a tracing direction parallel to the X-axis, from a tracing start point Ps1, and when a stylus comes into contact with a wire limit 1, the stylus senses the line, a predetermined amount of a pick feed 13a is effected from the point P1 to a point Pa1, and the tracing is again carried out along a path 12b which is parallel to the X-axis and extends in a direction opposite to that of the path 12a. Thereafter, a not shown model configuration is traced by sequentially executing a pick feed 13b, path 12c, pick feed 13c . . . . Note that a tracing direction of the above respective paths may be set at a predetermined angle to the X-axis direction or the paths may be traced in the Y-axis direction.
Nevertheless, according to this method, the start point Pa1 of the path 12b is positioned inward of the wire limit 1, whereas the start point Pa3 of the path 12d is positioned outward of the wire limit 1. Therefore, tracing cannot be accurately carried out within a region enclosed by the wire limit 1, and thus the tracing accuracy is poor.
As a method of solving this problem, the method shown in FIG. 3 (b) can be used, in which tracing is carried out from the start point Ps1 to a point Pb1 along a path 22a traveling in a direction that is at an angle .theta.1 with respect to the X-axis, whereby the tracing is carried out in parallel to the line segment P1-P2 of the wire limit 1. Thereafter, the tracing is carried out from the point Pb1 to a point Pb2 along a path 22b traveling in a direction that is at an angle .theta.2 with respect to the X-axis, whereby the tracing is carried out in parallel to the line segment P2-P3 of the wire limit 1. Subsequently, the tracing is carried out in a similar way by combining paths traveling in different directions.
When, however, the configuration of the wire limit 1 is complex, the number of paths is greatly increased, which requires a complex program and increases the tracing time.